1. Field of the Invention
The present invention applies to the field of radio communications systems and, in particular, to logical traffic and access channels.
2. Description of the Prior Art
Some radio communications systems, such as cellular voice and data communications systems, have several base stations in different locations available for use by mobile or fixed user terminals, such as cellular telephones or wireless web devices. Each base station communicates with a user terminal using a communications channel. For example, a communications channel may consist of a time slot in a TDMA (Time Division Multiple Access) frame on a physical carrier frequency. A TDMA frame may contain, for example, three uplink (user terminal to base station) time slots followed by three downlink (base station to user terminal) time slots, or vice-versa. The time slots may be used to transmit communication bursts, or they may be delineated on a continuous signal.
A physical carrier frequency may be a 625 kHz band around a central frequency, such as 800 MHz or 1.9 GHz. Thus, a base station transmits to a given user terminal, for example, on the second transmit and receive time slots on this carrier frequency in a given frame. Furthermore, the communications channel, also known as the conventional channel or conventional communications channel, may be organized using common duplexing techniques, such as FDD (Frequency Division Duplex) and TDD (Time Division Duplex), and common multiple access techniques such as FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access) and CDMA (Code Division Multiple Access). The channel may further be organized according to a hopping function indicating alternating resources over time.
Furthermore, in typical radio communications systems, the user terminals register with a base station prior to being able to access the resources of the base station, such as the channels of the base station or connections available through the base station. For example, before a wireless web user terminal is allowed to connect to an Internet service provider (ISP) using the channel resources of a base station, the user terminal must register with the base station. The registration may take place at the base station, or further upstream, for example, at a network box or ISP.
After the user terminal registers with the base station, it can request access to the base station and the resources associated with the base station. In a typical system the user terminal requests access on a designated access control channel, and the base station assigns another channel for future communications using this control channel. This designated access control channel uses a conventional communications channel described above. Since this channel is used only for access, it is not used for traffic data and is an overhead channel that decreases the efficiency of the communications system.